A typical flow-type ice manufacturing machine utilizing circulation of water on cooling panels is disclosed in Japanese Patent Early Publication No. 62-141478. Such machine will be referred to as flow-type ice manufacturing machines.
The above publication teaches an ice manufacturing :machine having an ice making unit consisting of a condenser unit and a refrigeration portion. The ice making unit is mounted on an ice storage portion. The ice storage portion has a machinery room for the ice making unit at the upper rear end of the storage portion, and the refrigeration portion in front of the ice storage portion. FIG. 12-14 shows ice manufacturing machine having the essentially same structure as disclosed in the above publication.
A typical ice manufacturing machine will be outlined below with reference to FIG. 12, since those machines shown in FIGS. 12-14 are essentially the same in structure. An ice engine or ice making portion 1 has a pair of ice making panels 2 having waving surfaces, a cooling pipe 3 mounted on the back sides of the ice making panels 2, a source -source water sprinkler 4, an ice removal sprinkler 5 for sprinkling water to remove the ice formed on the ice making panels 2, and a water circulation system 9 for circulating water in a tank 7. The tank 7 serves as a reservoir for receiving and storing water which has run down on the ice making panels 2 and falling into a conduit 5. The water stored in the tank 7 is pumped by a pump P back to the source-water sprinkler 4 to be sprinkled again by the source water sprinkler 4. Provided in a machinery room 11 is a condenser unit 17 which includes such elements as an electrically driven compressor 13 connected with the cooling pipe 3 and a coolant tube 12 to form a cooling cycle, a condenser 14, a condenser fan 15, and a capillary tube 16. Also provided in the machinery room 11 is an electric instrumentation box 18 accommodating a controller for controlling the operation of the cooling cycle as well as the operation of a water supply unit for the ice making portion 1. Also provided in the machinery room 11 are a hot gas circuit which has a hot gas valve 19 for use with the cooling cycle, and a water supply tube 22 which has a water supply valve 21. The ice making portion 1 and the machinery room 11 are partitioned by a thermal insulation partition 24. The ice making portion 1 is covered with a thermal insulation cover 25. The cover 25 has openings in its bottom and rear portions.
An ice storage chamber 27, covered with a thermal insulation wall, has a front opening 28 having a door 29. The ice may be taken out from this door 29. The front door 29 is provided with a door mask 30 on the back thereof. An ice guide 32 is provided in the ice storage chamber 27 for guiding ice pieces i dropping from the ice making portion 1 into the ice storage portion 27A. An ice level sensor 38b (which is of a thermostat type) is mounted on either side walls of the ice storage chamber 27 for detecting the amount of the ice stored in the ice storage portion 27A and for generating signals required in controlling the operations of the cooling cycle and water supply unit. A door mask stopper 34 is mounted on the upper edge of the front opening 28.
Unfortunately, the machine shown in FIG. 12 has several disadvantages. First, it stores ice pieces i heaping in the ice storage chamber 27 as outlined by a shaded line "a". However, the ice pieces at the top of the heap would fall on the front door 29, forcing the front door 29 to open or spill when the door 29 is opened.
In order to prevent such problems as discussed above, it is necessary to provide an ice guide 82 for guiding the ice pieces i falling from the ice making portion 1 to rear slope of the heap, or to provided a door having more resistive power against the pressure of the ice pieces i.
Such ice guide 32, however, induces another problem that it blocks the movement of a scoop taking up ice in the storage area 27A.
Second, the ice level sensor 33b mounted on the side wall near the front opening 28 can be easily damaged by a user's scoop hitting sensor 33b.
One might think, an attempt to avoid damaging the ice level sensor 33b, that it may be substituted for by an infrared type ice level sensor 33c mounted on the lower rear surface 27b of the ice storage chamber 27, as shown in FIG. 13. Such ice level sensor 88c, however, would be inadequate to detect the true amount of the ice i in the ice storage chamber 27, because, as shown in FIG. 14, the ice level sensor 33c would detect an apparent level of ice not indicative of the true amount thereof, and hence fails to resume ice making operations.
Third, a further disadvantage can arise in connection with the structure of such flow-type ice manufacturing machine as described above. In the case of flow-type ice manufacturing machine, it has two major portions, i.e. the ice storage chamber and the ice making portion mounted on top of the ice storage chamber. The ice storage chamber and the ice making unit (portion) have flat top surface and flat bottom surface, respectively, and the ice storage chamber is secured to the ice making unit (portion) by means of coupling members (such as mounts 18 as shown in FIG. 2 of the publication) and screws tightened horizontally (such as screws 15 shown in FIG. 2 of the publication). Use of such extra coupling members and screws, however, increases the total number of elements of the machine and add structural complexity to the flow-type ice manufacturing machine. Further, the top surface of the ice storage chamber is not necessarily secured to the ice making unit (portion)in the vertical direction.
Japanese Patent Early Publication No. 1-200168 discloses a specific structure of an ice making unit(portion). This unit has ice making panels having waving surfaces for making ice (hereinafter referred to as ice making surfaces) with their crest portions and trough portions extending horizontally, and a cooling pipe vertically zigzagging on the back side of the ice making panel. As the ice making surface is supplied with water from a source-water sprinkler, the water freezes on the recessed portions or trough portions of the panels. The ice thus formed is liberated from the ice making panels by the heat given off by a hot gas passed temporarily in the cooling pipe and ice removing water supplied by an ice removal sprinkler to the ice making panels.
Any highly efficient flow-type ice manufacturing machine must be capable of making sufficient amount of uniform ice pieces in one single short ice making operation. In order that a flow-type ice manufacturing machine satisfies such criteria, it must allow the ice making water to flow uniformly and smoothly in contact with the ice making surface. It is also important that the ice removing water must flow on the inner surfaces of the ice making panels. In addition, it is important that the cooling pipe is in good contact with the ice making panels to establish good heat transfer between them.
Further, the ice formed on the ice making panels must be easily liberated. All these conditions must be met for realization of a satisfactory ice making unit (portion) for use with a flow-type ice manufacturing machine.
Therefore, there is a need of ice making unit having improved efficiency for use in flow-type ice manufacturing machines.
A further improvement in the efficiency may be attained by providing a control system that has accurate response to the amount of the ice stored in the storage chamber, so that ice making operations are promptly resumed as the amount if the ice decreases to a specified level.
One type of control system intended for such purpose as mentioned above is disclosed in Japanese Utility Model No. 54-15351. This control system involves an ice storage chamber for receiving and storing ice discharged from its ice making engine. The ice storage chamber has an electrically grounded metal case (which can be an inner/outer box of the ice storage chamber) serving as a first electrode, and an electrically insulated ice level sensor mounted on the inner wall of the ice storage chamber serving as a second electrode. These two electrodes and the space between them constitutes an electric capacitor. Its electric capacity varies with the amount of the ice stored in the ice storage chamber. The change in capacitor is transformed into an electric signal, which is applied to a control circuit controlling the operation of the ice manufacturing machine.
It is important that the ice level sensor is electrically insulated from other elements such as conductive frames of the ice storage chamber so that the change in capacitor takes place only when the ice heaps up to a predetermined level in the ice storage chamber to touch the sensor.
This type of sensors, however, have drawbacks in that their electrodes can be electrically short-circuited by dust and deposit accumulating between the electrodes, thereby resulting in erroneous control signals. As such the sensor is desirably mounted physically off the case, which is, however, difficult to do.